1. Field of the Invention
The present invention relates to novel processes for the production of red phosphorus and the novel products of that process.
2. Background Information
Red phosphorus may be produced from white phosphorus by maintaining the white phosphorus at an elevated temperature which is usually in the range 220.degree. to 280.degree. C. Conventional processes for the production of red phosphorus utilise lengthy reaction times in order to convert the white phosphorus to red phosphorus as completely as possible. Such procedures can be operated as batch processes and produce a brittle form of red phosphorus which must be chipped out of the reaction vessel and ground in a mill. The product may contain residual unconverted white phosphorus which constitutes a fire risk when the product is exposed to the atmosphere. It is then necessary to treat the product with alkali in order to remove the white phosphorus.
The production of red phosphorus from a slurry of red phosphorus in molten white phosphorus by sweeping the slurry with inert gas at temperatures above 200.degree. C. so as to volatilise the white phosphorus, has been described by P. Miller, R. A. Wilson and J. R. Tusson in Industrial and Engineering Chemistry Volume 40 (1948) p 357 to 366. Such procedures offer clear advantages when compared to the conventional processes in that they can be operated on a continuous basis, but are complicated by the difficulties of completely separating the white phosphorus and the red phosphorus in a manner which avoids the deposition of solid red phosphorus in the processing equipment. Miller, Wilson and Tusson state that centrifuging the slurry was not effective and that vacuum distillation of the slurry was not satisfactory because of the difficulty in removing the last traces of white phosphorus from the residual red phosphorus.
In U.S. Pat. No. 3,998,931 Hyman and Chase describe a process for the production of a slurry of red phosphorus in white phosphorus which they state is useful in the production of red phosphorus. However, no indication whatever is given as to the method by which the red phosphorus is to be separated from the white phosphorus.